1. Field of the Invention
The present invention relates to a recirculating automatic document feeder (RADF) or recirculating document handler (RDH) used for sequentially feeding the original documents to an exposure region in various optical reading units such as electrostatic copying apparatus and image scanner.
2. Description of the Prior Art
When copying images on face and back sides of a plurality of original documents automatically and continuously, the documents finishing the copying process for the images on one side must be inverted upside down, and the images on the opposite side must be subjected to copying process again. For this purpose, the conventional copying apparatus is provided with a so-called RADF having means for switching back or for inverting the leading and trailing edges of the documents only by a reciprocating motion, in part of the conveying route composed in a loop shape. In such RADF, a plurality of documents are placed on a hopper, and the documents are led out to the exposure region one by one, and the documents finishing the copying process for the images on one side are inverted by the switchback means to be returned to the hopper. By performing this process continuously for the number of documents, the copying process of the images on one side of the documents placed on the hopper is completed. At this time, the plurality of documents are placed on the hopper in the state upside down from the initially installed state. When the documents placed in the inverted state are led to the exposure region, the opposite side of the surface exposed in the first copying process is exposed, so that the opposite side may be subjected to an exposure process. By inverting the documents finishing the second copying process by the switchback means and returning to the hopper, the documents finished in copying process on both sides are put on the hopper in the initial state.
In such conventional RADF, however, since the documents finishing the first copying process are inverted and put on the hopper, when attempted to repeat the first copying process due to jamming occurring in the copying process, the job to return the documents to the initially placed state is bothersome.
To eliminate this problem, it has been proposed to use two hoppers, in which the documents finishing the copying process of the images on one side are placed in a second hopper from the first one initially put on, and in the second copying process, the documents are fed from this second hopper, and the documents finishing the copying process of the images on two sides are returned to the first hopper. In this method, since two hoppers are used, the size of the apparatus increases.
A typical prior art is shown in FIG. 1, in which a recirculating automatic document feeder (RADF) 1 is mounted on the upper surface of a main body 2 of electrostatic type copying apparatus so as to be free to be dislocated angularly about a rotary shaft 3. On the upper surface of the main body 2 is disposed an original platen 4 made of hard glass or the like on which the document is placed by the operator when the RADF 1 is not used. While the automatic document feed by the RADF 1 is not effected, the exposure means (not shown) which is incorporated in the main body 2 and is designed to expose by scanning the document is conveyed by the driving means in the copying apparatus main body, and the document put on the original platen 4 in this way is scanned and exposed in one direction from its one end to the other end.
On the other hand, when the automatic document feed by the RADF 1 is conducted, the exposure means is stopped at a position for exposing the exposure region 4a. In the RADF 1, on an original hopper 5 on which the original documents can be stacked up, a plurality of paginated documents having images formed on both sides and are sequentially placed with the first page on the top. Such state is schematically shown in FIG. 1, in which encircled numerals 1 to 4 denote the page numbers attached to the documents.
The plurality of documents placed on the original hopper 5 are sequentially drawn out from the bottom side one by means of paper feed belt 8 entrained on rollers 6 and 7 rotated and driven by driving means such as a motor which is not shown, and are led to a conveying route 9 one by one. The conveying route 9 extends in the widthwise direction of the original (the direction perpendicular to the sheet of paper of FIG. 1), and the section perpendicular to the widthwise direction is approximately semicircumferential and is uniform in the widthwise direction, and its outlet is located near one end of the original platen 4.
In relation to the original plate 4, a conveying belt 14 is entrained on rollers 10, 11 and is circulated and driven in the direction of arrow 12. This conveying belt 14 functions as means for pressing the documents onto the original platen 4 when copying them while documents such as a book are placed on the original platen 4 without using the RADF 1. When the RADF 1 is activated and the documents are fed automatically, the documents coming from the outlet of the conveying route 9 are conveyed through a route 15 between the conveying belt 14 and the original platen 4 by the frictional force between the conveying belt 12 and the document surface. In this way, the documents are sequentially led into an exposure region 4a.
Relative to the exposure region 4a, an original drum 16 in a shape of right circular cylinder having an axial line extending parallel to the exposure region 4a is disposed. The original drum 16 is rotated and driven in the direction of arrow 17 by driving means which is not shown, and the document coming out of the route 15 is taken up on the original drum 16 by the function of driven roller 18 and others and is conveyed.
Near the driven roller 18, the conveying route is branched into a conveying route 19 and a conveying route 20. In relation to the branching position is disposed a gate flapper 22 which is angularly dislocated by driving means containing a solenoid and other elements (not shown) around a rotary axial line 21, and is designed to lead the document to either one of the conveying routes 19, 20. The document coming out through the conveying route 19 is conveyed as being taken up on the original drum 16, and is returned to the original hopper 5 from the conveying route 23. The returning document is put on the top of the stack of documents in the original hopper 5.
The document led into the conveying route 20 contacts with a roller 24, and is held between this roller 24 and a roller 25 disposed in relation to the conveying route 20, and is further sent into a conveying route 26. Relative to the conveying route 6, a roller 27a rotated and driven in normal and reverse directions, and a driven roller 27b contacting with this roller 27a are disposed. Being branched off from the conveying route 26, a conveying route 28 continuous with the conveying route 23 is provided. In relation to this conveying route 28, a roller 29 contacting with the roller 24, and a pair of rollers 30 are installed. At the position where the conveying route 28 is branched off from the conveying route 26, a gate flapper 31 for leading the document sent to the conveying route 26 further into the conveying route 28 securely is provided.
The document set to the conveying route 20 is carried in the direction of arrow R1 until its trailing edge passes through the branching part of the conveying routes 26, 28 due to the rotation and driving of the roller 27a. When the document is conveyed up to the position of passing through the branching part, the rotating direction of the roller 27a is reversed. At this time, the gate flapper 31 is angularly dislocated in the direction of arrow R2 around a rotary axial line 32. As a result, the document is conveyed in the direction of arrow R3, and is led into the conveying route 28 by the function of the rollers 24, 29, and others.
The document coming from the conveying route 28 is guided by the conveying route 23, and is put on again from the top side on the original hopper 5 by the function of the pair of rollers 33.
For exposing the both sides of the plural documents stacked on the original hopper 5, first the documents are circulated, one by one, in a loop of conveying route 9, conveying route 15, and conveying routes 20, 26, 28, 23. In this way, the document surfaces of all odd pages of all documents stacked on the original hopper 5 are exposed. After the first feeding cycle of the documents for exposure, the documents are stacked on the original hopper 5 with the odd pages down.
In the second feeding cycle of the documents for exposure, it is the even pages that are exposed in the exposure region 4a. In this case, too, same as in the first feeding cycle, the documents are circulated in a loop of the conveying route 9, route 15, and conveying routes 20, 26, 28, 23. When the second feeding cycle of exposure is thus over, the plurality of the documents are stacked up on the original hopper 5 in the same state as in the initial state.
To expose the documents plural times continuously, the documents are led into the conveying route 19 by the function of the gate flapper 22 from the route 15, and are taken up on the original drum 16 and conveyed. In this way, the same side of the documents is exposed plural times in the exposure region 4a.
In such prior art, the documents finishing the first feeding cycle of the documents for exposure are stacked up on the original hopper 5 upside down in the initial state. Therefore, if attempted to repeat the exposure due to, for example, jamming in the conveying routes 9, 20, 23, 26, 28 or route 15, the job to restore the documents into the initial stack-up state is bothersome.